Persons with limited ability to walk are dependent on wheelchairs. Wheelchairs are required by persons who are no longer able to walk longer distances or are unable to walk at all. However, persons of either group may retain a certain residual mobility that enables them to transfer themselves, e.g., from the wheelchair into a bed or another chair, independently, i.e., without the assistance of another person. This is achieved by moving the wheelchair as close as possible to the piece of furniture in question. After the disabled person has transferred himself from the wheelchair to the other piece of furniture, the wheelchair naturally remains at its original location where it was vacated. This is occasionally quite bothersome.
Similar problems arise if a disabled person transfers himself from the wheelchair and into a vehicle. The wheelchair subsequently must be stowed in the vehicle by means of crane-like apparatuses, or the like.
The wheelchairs used in such instances consist of a chair frame that is constructed with the least weight possible and carry a seating surface and a backrest. Two large running wheels are rotatably supported on the chair frame coaxially with one another. The shafts of these wheels are approximately situated in an extension of the backrest, wherein two small support wheels are provided on the frame at the back of the knees of a user. The support wheels can be passively steered.
The large running wheels simultaneously serve for driving the wheelchair. In this case, the outer side of each wheel is provided with a gripping ring that is connected to the wheel without rotational play. The user takes hold of these rings with his hands in order to set in motion and steer the wheelchair. This type of wheelchair is completely passive or manually operated.
In addition to passive hand-operated wheelchairs, self-propelled wheelchairs have also been introduced into the market. These wheelchairs feature a chassis that is constructed similar to a motor vehicle. The steering wheels and the driving wheels are of approximately the same size and are relatively small in comparison with the wheelchair. The wheelchair furthermore carries an electric drive system and heavy batteries in order to set in motion the wheelchair and its occupant.